Collapsible tubes formed of metallic and plastic materials have long been known in the packaging field. Extruded metal tubes are inherently brittle and repeated use not infrequently results in wall cracks so that product is exuded from a location other than the essentially rigid dispensing orifice. Of the prior art metal tubes, aluminum tubes, while probably being the least brittle, are somewhat limited in their applications since up to the present time it has not been possible to apply to the interior surfaces thereof a completely satisfactory coating, when required to prevent attack and corrosion of the metal by alkaline or acid contents and contamination of the contents by the reaction products. Notwithstanding the relatively brittle nature of a metal tube, the mentioned internal coating operation requires an additional processing step which necessarily increases the cost of the final article.
Tubes formed of polyethylene and other plastic materials have enjoyed wide commercial success in the packaging of many products; however, certain other products after a time have been noted to deteriorate when contained therein. Plastics as exemplified by polyethylene are permeable to a degree when employed in the wall thicknesses used in tubular containers, and the essential oils embodied in most dentifrices for flavoring purposes are reduced in volume during storage of the container, rendering the dentifrice less palatable. Also, the plastic container wall absorbs oxygen over a period of time and ultimately may decompose the product, which has actually been found to be the case with fluoride-containing toothpastes. A further disadvantage of a plastic tube resides in the inability of the surface to readily receive printing or decorative material. In addition, plastic tubes, as exemplified by polyethylene, have a memory effect; that is, they do not remain compressed when squeezed, a particular disadvantage for dentifrice tubes.
To counter the above problems, it has accordingly been proposed to provide a metallic foil barrier between the product and the polyethylene tube body. This would counter the compressibility problem in that the metal layer would impose its compressibility upon the plastic. In addition, the metallic foil barrier between the product and the polyethylene tube body would prevent the mentioned loss of essential oils and the absorption of oxygen. The metallic barrier has been suggested as an interlayer between facing sheets of polyethylene, and that a laminate be formed by heat with or without suitable adhesives. However, while a structure of this general character is effective to prevent some product permeation and oxygen absorption through the tube body, and particularly when the inner thermoplastic layer is a copolymer of ethylene and a polar group containing monomer which is co-polymerizable therewith, there remains the possibility of product deterioration albeit to a much lesser extent.